When I'm trying to run it on my android phone directly, nothing happens. After "debug:" doesn't write anything. Its not even detecting the device: Android > Select Device > "No connected devices". The computer recognized it (in My Computer > Portable Devices) when I pluged the USB in... and yes, I activated the "USB debugging mode" on my phone.
Sorry if I wrote anything incorrectly, English is not my mother language. I hope somebody can help me. :((

In the toolbar, click Debug for the Select Deployment Target window.
afterwards you need to either connect a device via USB or click Create new virtual device to use the Android Emulator.

In case you see a dialog asking if you want to "switch from Run to Debug," that means your app is already running on the device and it will restart in order to begin debugging. If you'd rather keep the same instance of the app running, click Cancel Debug and instead attach the debugger to a running app.